With the variety of weapons on offense, the speedy receivers, the strong, effective running backs and the strong-armed quarterback, another factor has been dictating how the Trojans call and execute their offense.

Tuesday after practice at Howard Jones Field, USC head coach Pete Carroll said his defense's success has been a driving factor in how the Trojans have chosen to attack teams offensively.

"It's taken us awhile to get through the schedule to get a sense of what we could do. Not until the last couple of weeks, like the Arizona week, we started to get a sense of what we're doing and what we're capable of doing," Carroll said. "We played to our defense entirely this past week, and it worked out fine."

Against Cal, the Trojans had supreme confidence that the Bears would not be able to establish a long scoring drive, meaning the offense was extra careful not to give up the ball with a short field at stake.

"The biggest factor is to know how difficult it is to go 80 yards against our defense," offensive coordinator Steve Sarkisian said. "If you give them the ball on your 30, they only have to hit two passes and it's a touchdown.

"It makes a team's defense not as good as it could be, and it makes the other team's offense better than they are."

Even quarterback Mark Sanchez said he's had to learn how to quarterback with such a dominant defense waiting to get on the field.

Sanchez has had to repress some of his urges to throw the ball down the field and take unnecessary risks.

"When you have a strong defense like this and such a good running game, it's OK to punt. It's not the end of the world," Sanchez said. "It's hard to hold back the way I love to play, that street football mentality where you just wing it all over the field.

"I'm starting to get a handle on it."

And as Sanchez's understanding in how the defense can be relied upon has increased, so has Carroll's.

"It does affect us." You have to get to where you know. Until then, you're guessing," he said. "At this point, we're consistent. We're running the ball well, and we know that it's going to be hard to score fast on us."

The Starting Line

At Oregon State, the Trojans fell behind quickly and were forced to work against a deficit and a hyped crowd.

Carroll said he thinks a quick start to keep the Stanford crowd out of the game could be crucial come Saturday.

"I think it always is, particularly on the road," Carroll said. "You hate to have to give up the crowd to them by their ability to do good things and capture the crowd and take advantage of that.

"You hope you play well and consistently early so you don't give them the advantage. We saw that very clearly weeks ago. But that doesn't necessarily settle the game. You'd like not to have to deal with that if you can help it."

Triple threat

Freshman D.J. Shoemate took reps with the service team as running back, marking the third different position he's played this year - in addition to fullback and wide receiver.

"I get to utilize my talents many different ways. Truly, it's a blessing," Shoemate said. "I'm just going to do whatever I have to do for the team and to better myself as far as learning the offense.

"I know three positions now."

Extra Points

• The optimism surrounding Kevin Ellison's return after knee surgery early last week seems to have been slapped in the face with some realism.

Ellison, who said he hoped to be ready last weekend for Cal, will not play this Saturday at Stanford either.

The swelling in his right knee has dramatically decreased, though, and he said he's been working on strengthening and stretching the knee.

"It sucks not playing," he said, "but it is what it is."

• Joe McKnight missed Tuesday's practice to attend services in Louisiana for his late grandmother, who passed away before Saturday's game with Cal. Carroll said he expects McKnight back in Los Angeles late Tuesday night.